1. Technical Field
Disclosed embodiments relate to a direct current (DC) circuit breaker and a circuit breaking method thereof and, more particularly, to a DC circuit breaker which can improve a high switching operation during a circuit breaking operation as well as block a DC current in a safer and more efficient manner, and a circuit breaking method of the DC circuit breaker.
2. Description of the Related Art
When a fault occurs in a power system, a fault current is blocked through a circuit breaker in order to protect power devices and equipment. When a failure occurs in a system, an electric relay determines a failure state and sends out a trip signal for opening to the circuit breaker. After receiving the trip signal, the circuit breaker opens a contact point of the circuit breaker where the fault current flows by using a driving device in order to block the current. In the meantime, an arc current comes to flow at both terminals of the circuit breaker and this fault current will keep flowing due to the arc current unless a sufficient insulation condition is established on the contact point. As for an alternating current (AC) system, the current passes through a current zero point at a constant period, and the arc current will extinguish when the current reaches zero to block the fault current as well as a sufficient contact point distance is guaranteed. However, as long as a direct current DC system is concerned, it is very hard to extinguish the arc current since there is no current zero point. Generally, it is possible to block the DC fault current by spreading the arc at a voltage not greater than 3000 V, while it is hard to extinguish the arc current when the voltage is higher than that. Therefore, a technology, which blocks the fault current by emulating a current zero point as in the AC system by using various ways, is required. By using DC circuit breaking technologies which have been developed up to now, there are circuit breakers which are developed by using one of: a reverse voltage type in which the arc generated at the contact point is spread; a resonance type in which a separate resonance circuit is formed to cause resonance by using the DC current; a reverse current type in which parallel capacitors are precharged by charges such that, when a failure occurs, the charges are applied in a direction opposite to that of the arc current to block the arc current through current superposition; and power semiconductors which can be turned on and off.